In the past, much effort has been devoted to the development of utility tool devices. The desirable qualities of such a device fall into several categories including safety, reliability, durability, versatility and convenience of use.
Carson (U.S. Pat. No. 2,674,286) is directed to a retractable tool with a double ended shank. However, a disadvantage of the device of the Carson patent is that the tool disclosed has a single side locking design and does not prevent the shaft from completely sliding out from the handle. This design is not effectually advantageous to the user as it is not stable.
Johnson (U.S. Pat. No. 2,612,489) discloses a retractable tool with a handle. However, a disadvantage of the Johnson patent is that the tool disclosed has a shaft that must be grasped by the user and pulled towards him in order to release the locking mechanism. This mechanism is simply not an efficient means for unlocking the shaft from the handle. Johnson's locking means also does not provide a stable means for securing the handle to the shaft of the tool. The parts protruding from the shaft may cause difficulty in operation.
Zilliox (U.S. Pat. No. 1,689,376) discloses a multi bit tool with a clamping screw which is loosened or tightened to expose a screwdriver tip for use. A disadvantage of Zilliox's invention requires another tool to manipulate the clamping mechanism. Also, Zilliox clamping mechanism is cumbersome to use and over time the threads on the screws may wear causing structural damage to the locking mechanism.
Clifford (U.S. Pat. No. 814,020) discloses a screwdriver with a double ended shaft. However, similar to Zilliox, Clifford also discloses a screw mechanism which is cumbersome to use and over time the threads on the screws may also wear causing inefficient operation of the tool.
The available tools, such as those noted above, provide varying degrees of dual operation. This feature however, is gained at the expense of versatility and convenience. In accordance with the present invention, these and other disadvantages of the prior art are minimized. The present invention provides a high degree of fail-safe operation of a dual function tool while remaining versatile and convenient to use.